It was a very dry summer in much of the Northeast, with moderate to severe drought in parts of NY. But the region is nothing if not variable in weather conditions; I talked with a Vermont farmer who’d harvested four excellent cuts of alfalfa by the end of August and said he was looking at a “huge” corn crop. He isn’t going to take a fall alfalfa harvest because he already has more than enough forage. But combine dry weather and impending corn harvest for silage and there’s always talk of nitrate poisoning. But talk is about all we usually wind up with since rarely are there actual cases of nitrate poisoning of livestock. We can’t ignore the potential for problems because nitrate toxicity is a serious matter, but fortunately it’s also a rare one—at least in the Northeastern U.S. That’s for three reasons: First, the fermentation process reduces nitrate concentrations by about 50%, one more reason for farmers to make sure that their corn is completely fermented before attempting to feed it. Second, with the cost of fertilizer, most farmers can’t afford to apply enough fertilizer N to result in very high nitrate levels. Heavily manured may be the exception, but in much of this region manure is applied to corn fields in the fall so by the time the following summer rolls around much of the readily-available N is long gone. And third, nitrates concentrate in the bottom of the stalk. Unlike California and other parts of the Left Coast where corn is often chopped at a 2” stubble height, farmers in the Northeast (where stones are a fact, not a rumor) most corn isn’t chopped at anything less than about 6”. In fact, most farmers who think they chop at 6” haven’t actually measured it with a ruler. I’ve found that 8” stubble height is a lot more common than 6”.
This is similar to my experience with prussic acid poisoning, which is a reported threat when summer annuals such as sudan-sorghum are harvested either too early or too soon after a killing frost. Warnings about the potential for prussic acid poisoning almost always accompany any recommendations or discussions about summer annual crops, but in fifty years of working with farmers in the Northeast I can’t remember one time when cattle were actually poisoned by prussic acid. And it’s not because farmers always closely follow recommendations either!